Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

4th year medicine > PH and EBM > Flashcards

PH and EBM Flashcards

1
Q

PICO

A

patient/ population
Intervention/ treatment
Comparison/ alternative treatment
Other relevant clinical info

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

types of observational study

advantages and disadvantages

A

observational:

  • ecological
  • cross sectional
  • case-control
  • cohort study

advantages:

  • ethics (can’t force a group to smoke)
  • can use very large groups

disadvantages:

  • biases
  • confounding (links an exposure with an outcome)
  • reverse causality
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

cohort study

A

DONT HAVE ANY DISEASE AT START - see who develops disease with risk factors

  • exposure to defined factors measured at baseline
  • any new incidence of disease
  • high and low exposure individuals compared
  • calculate RISK RATIO
  • prospective or retrospective

advantages:

  • reduce reverse causality
  • reduces selection bias
  • allows testing of multiple outcome
  • better confounder control

disadvantages:

  • retrospective: recall and interviewer bias, reverse causality
  • prospective: LONG, LOSS TO FOLLOW UP bias
  • inefficient for rare diseases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

cross-sectional study

A

SNAPSHOT OF PREVALENCE

  • shows prevalence of disease in population at snap shot moment,
  • good for measuring true burden of disease
  • measure risk factors,
  • can’t measure incidence, susceptible to reverse causality
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

case-control study

A

WHAT IS CAUSE OF THE OUTCOME

  • recruit available cases and a comparable control group
  • sample determined by outcome
  • RETROSPECTIVELY assess exposure to potential risk factors - compare case and control
  • if exposure more common in cases, risk factor associated with increased disease
  • presented as ODDS RATIO

advantages:

  • only study comparing groups defined by outcome
  • good for RARE CONDITIONS
  • can test for multiple exposures

disadvantages:
- reverse causality
- selection bias: when selecting control group, choose suitable population, not one which would have higher/lower associations to exposure
- measurement bias:
recall bias- cases more likely to recall exposure as they understand disease
interviewer bias - can cause cases to recall more exposure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

systematic review

A
  • all relevant evidence on a given clinical question
  • minimise biases and random errors
  • highest quality of evidence
  • much cheaper and quicker than RCTs

disadvantages:

  • only as good as the studies they’re done on
  • reporting biases:
  • -> publication bias - statistically significant are more likely published
  • -> time lag - big studies published quicker
  • -> language - English get published quicker
  • -> multiple publication - big studies may be published in multiple places
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

p value

A

the probability of the observed results occurring just by chance, if the null hypothesis was true

very low p-value indicates strong evidence against the null hypothesis (differs in outcome to control)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

risk ratio vs odds ratio

A

risk ratio: out of total number of people in the study

odds ratio: out of unaffected patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

sensitivity vs specificity

A

sensitivity:
true positive rate - probability of a positive test in people with disease (proportion of all those with the condition)

specificity:
true negative rate - prob of negative test result in people without disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

primary prevention definition

A

prevent the onset of disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

secondary prevention

A

early identification and treatment of disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

tertiary prevention

A

rehabilitate people with established disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

prevention paradox

A

large number of small risk cases may get disease, but population interventions may provide little to individuals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

R number

A

effective reproduction rate - number coming from one case

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

R0

A

basic reproduction number R0 =
probability of effective contact x number of contacts x duration of infectiousness

better for planning for infectious diseases

(in a wholly susceptible population- scenario with no immunity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

cost effectiveness

A

cost per clinical effect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

cost utility

A

cost per QALY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

SMR ratio calculation

A

SMR =

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

example q:

condition present:
test +ve: 60
test -ve: 57
total: 117

condition absent:
test +ve: 1
test -ve: 400
total: 401

total +ve: 61
total -ve: 457

total people:
518

calculate sensitivity, specificity, positive predictive value, negative predictive value

A

sensitivity: 60/117
specificity: 400/401

positive predictive value: 60/61

negative predictive value: 400/457

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

positive predictive value

A

probability of having disease if you test positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

negative predictive value

A

probability of not having disease if you test negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

inverse equity hypothesis

A

new health interventions are initially adopted by wealthy/ educated, initially increasing inequalities as poorest/ less educated lag behind on uptake of the new health intervention

example: traffic light labelling of foods sold pre-packaged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

which mechanism is bias reduced by with using big groups (e.g. school) instead of individuals

A

contamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what aspect of trial quality is always feasible when comparing treatments in an RCT

A

allocation concealment

not: blinding (on either side), follow up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

best available evidence in order

A
  1. systematic review
  2. RCTs
  3. cohort studies
  4. case-controlled studies
  5. background info
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

ecological study

A

WHAT IS THE EXPOSURE CAUSING

  • average exposure plotted against rate of outcome
  • association btwn them
  • environmental or social exposures at population levels
  • disadvantages: ecological fallacy
    difficult to control confounding
    dependent on previously collected data
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is ecological fallacy?

A

disadvantage of ecological studies: the assumption that average characteristics apply to individual
e.g. smokers get cancer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

RCTs

A
  • interventional study
  • two arms one group exposed
  • participants consent

advantages:

  • evidence of causality
  • best confounder control
  • allocation concealment reduces selection bias
  • blinding reduces measurement bias

disadvantage:

  • sample size needs to be large enough
  • selection bias
  • performance bias
  • detection bias
  • attrition bias (unequal loss of participants)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

meta analysis

A

statistical analysis - combing results of independent studies
- similar intervention, similar outcome, similar populations

fixed (common) effect:

  • assumes true effect is the same in each study.
  • the only variation in estimates is sampling error. (assumes all studies are trying to show the same thing- homogeneity)
  • less weight given to small samples

random effects:

  • estimates mean effect (assumed that the true study effects vary- not showing same effect - heterogeneity).
  • info from small studies matters more

heterogeneity:
- suggests treatment effect is context dependent (all studies not showing same effect)

funnel plots asymmetry:
- publication/reporting bias, poorer quality studies –> extreme treatment effects

30
Q

what methods are used for qualitative studies

A

for helping understand why something happened

  • observations
  • interviews
  • focus groups
  • documents
  • oral history
31
Q

what data analysis is used for qualitative studies?

A
  1. familiarisation with data
  2. coding (repeated ideas)
  3. searching for themes
  4. reviewing themes
  5. defining and naming themes
  6. writing up
32
Q

performance bias

A

affects RCTs

systematic differences in the care provided to members of different study groups other than the intervention

33
Q

detection bias

A

affects RCTs

systematic differences btwn groups in how outcomes are determined

34
Q

attrition bias

A

affects RCTs

if the numbers lost to follow up are not the same in each group

35
Q

intention to treat analysis

A

done to avoid the effects of crossover and dropout

comparison of the treatment groups that includes all patients as originally allocated after randomization

36
Q

per protocol analysis

A

instead of intention to treat analysis

comparison of treatment groups that includes only those patients who completed the treatment originally allocated

37
Q

reporting biases

A
  • publication bias- statistically significant are more likely to be published
  • time lag - big studies published quicker
  • language - English studies quicker
  • multiple publication - in bigger studies
38
Q

forest plots

A

fixed or random model
pulled odds ration
with 95% CI tails

diamond: overall odds ratio in the middle with overall 95% CI on the ends

39
Q

funnel plots

A

to show whether there is publication bias

  • used in SRs and meta-analysis
  • asymmetric (if part not filled in, they haven’t been published –> publication bias)
40
Q

prevalence calculation

A

total patients with disease in population

individuals w disease
/
total population at risk

41
Q

incidence

A

new cases in given period
/
population at risk initially disease free

42
Q

incidence rate

A

(# new cases of disease)
/
(population at risk) x time interval)

43
Q

risk

A

patients w disease
/
population

44
Q

risk ratio

A

risk of outcome occurrence in exposed
/
risk of outcome occurrence in unexposed

likelyhood of disease with exposure compared to without exposure- strength of association not causality

RR> 1 exposure predisposes outcome

RR<1 exposure protects against outcome

45
Q

risk difference

A

risk of outcome in exposed - risk of outcome in unexposed

46
Q

number needed to treat

A

1/ risk difference

number of patients that would need to be treated to prevent one case of the disease

47
Q

odds

A

patients with disease
/
patients without disease

48
Q

odds ratio

A

odds of having disease in exposed
/
odds of having disease in unexposed

49
Q

null hypothesis

A
  • no difference btwn case population and control population

- study aims to disprove null hypothesis

50
Q

p-value

A
  • the probability that differences in observed data would have occurred by chance
  • small p-value (p<0.05) = greater evidence against null hypothesis
51
Q

incremental cost-effectiveness ratio

A

= C/E
= (Ct - Cc)/ (Et - Ec)

TOTAL COST OVER QALY

C= cost
E= effectiveness
t = treatment 
c = comparator

compares treatment to comparator (next best)

52
Q

Quality Adjusted Life Year (QALY)

A

= (time spent in healthy state) x (quality of life weight)

53
Q

standard mortality ratio

A

= (# observed deaths / # expected deaths) x 100

  • ratio of observed deaths to expected deaths
  • SMR 100 = study pop has same number of deaths as standard pop
  • SMR > 100 more than expected # of deaths
54
Q

statistical power

A

probability of correctly rejecting null hypothesis when in truth the treatment has an effect

55
Q

net monetary benefits

A

= (E x lamda) - C

E= cost
lamda = willingness to pa for QALY 
C = cost
56
Q

95% CI

A

range of value within which we are 95% confident that the true population value lies

57
Q

+ve likelihood ratio

A

probability of a positive test in people with the disease/ probability of a positive test in people without the disease
= sensitivity/ (1-specificity)

used with layers monogram

58
Q

accuracy

A

(true positives + true negatives)
/
all results

59
Q

SpPin

A

when a test has a high specificity a positive result rules IN the target disorder

60
Q

SnNout

A

sensitivity - when a test has a high sensitivity a negative result rules out the target disorder

61
Q

spectrum bias in diagnostic testing

A

the types of patients recruited to the study

62
Q

work up bias in diagnostic testing

A

do all patients get both diagnostic and gold standard tests

63
Q

improving public health by health protection

A 
infectious disease
- childhood vaccination
- immunisation 
environmental hazards 
emergency response to infectious disease outbreaks
64
Q

improving public health by health promotion

A
  • develop primary promotion programme
  • health inequalities
  • behaviour change
65
Q

improving public health by health services

A
  • secondary prevention programmes e.g. screening
  • healthcare quality
  • health policy
66
Q

proportionate universalism

- what is it the solution to and what is it?

A

solution to prevention paradox

providing service universally but with increased intensity on disadvantaged

67
Q

vaccination programme types

A
  • universal rolling - give vaccine continuously to everyone of certain age when they reach it
  • universal catch-up - give vaccine to everyone in pop within a certain age range with a fixed time period
  • targeted - aimed at people who are high risk
68
Q

types of vaccine

A

live vaccine:

  • MMR, BCG, rotavirus, polio, influenza
  • strong immune response
  • can be administered via mucosal route
  • mild infection after
  • must be maintained alive (cold chain)

conjugate vaccine:

  • HiB, men C
  • development of immunity to non-protein material
  • smaller response

toxoid:

  • diphtheria, tetnus
  • no risk of infection

subunit
- pertussis, MenB

69
Q

health inequality vs health inequity

A

health inequality: differences in health

health inequity: unjust difference

70
Q

harms of screening

A
  • false negatives/ false reassurance
  • over detection - false anxiety
  • can increase incidence (picking up more less serious cases)
  • length time bias - leaves out poor prognosis (cause treated quickly)
71
Q

healthy screened effect

A

people who come for screening tend to be healthier than those who don’t

4th year medicine (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions